Question

Study the pictures below. Give the reason for the corrosion of these statues and state its causes created by nature and human activities.

 

Answer 1

The pictures show statues that have been corroded and damaged. The corrosion of these statues is caused by acid rain.

Reason for Corrosion:

Acid rain is defined as rainfall with a pH below 5.6. Acid rain corrodes buildings, monuments, metals, and rock structures. Acid rain is especially damaging to structures made of limestone or marble because the acid (mostly sulphuric acid) combines with the calcium carbonate in these stones, causing them to deteriorate over time. The reaction can be represented as follows:

CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂ 

The calcium sulphate formed is soluble in water and washes away, leading to loss of detail and ultimately the destruction of the statue's features.

Causes of Acid Rain by Nature:

1. Lightning: Lightning produces nitrogen oxides, which when combined with water form nitric acid.
2. Volcanic Activities: Volcanic eruptions emit sulphur dioxide and other gases into the atmosphere, contributing to acid rain.
3. Forest Fires: Natural forest fires produce sulphur and nitrogen oxides into the atmosphere.

Causes of Acid Rain by Human Activities:

1. Burning of Fossil Fuels: The burning of fossil fuels in factories, power plants, and automobiles accounts for around 80% of sulphur oxide emissions. Sulphur trioxide combines with water to produce sulphuric acid (H₂SO₄), which is the primary source (60-70%) of acid rain
2. Industrial Emissions: Factories emit sulphur dioxide, nitrogen oxides, chlorine, and hydrochloric acid into the atmosphere.
3. Vehicular Emissions: Automobiles emit nitrogen oxides and other pollutants, causing acid rain.
4. Power Plants: Thermal power plants that burn coal emit enormous amounts of sulphur dioxide.